The present invention relates generally to an optical system and more particularly to a lightweight optical system which may be worn on the head for transposing viewed images.
Image transposing devices have been used in the psychophysical and behavioral effects of many forms of motion sickness. Such devices produce a reversal of compensatory eye movements. Wearing such an image transposing device may create motion sickness symptoms. These symptoms include, for example: 1) dizziness; 2) vertigo; 3) flushing; 4) sweating; 5) excessive salivation; 6) pallor; 7) dryness of mouth; 8) tachycardia; 9) stomach awareness; 10) stomach discomfort; 11) queasiness; 12) vomiting; 13) spatial disorientation; 14) fine and gross motor incoordination; 15) disequilibration; 16) misreaching; 17) tremor; 18) temporary cognitive deficits; and 19) short-term memory problems.
The study of such symptoms is particularly important since a combination of several of these symptoms may provide researchers with an ability to simulate the combination of symptoms which appear in some human disorders. For example, symptoms 13 through 19 listed in the preceding paragraph are equivalent to Parkinsonism-like effects. Similarly, symptoms 1-18 may be observed and simulated by researchers investigating space motion sickness, airsickness, seasickness, and ground-motion sickness. The device allows use by animal subjects, e.g., rethesusi or macaque monkeys.
Another aspect of the research involving the use of image transposing devices is investigating the ability of subjects to adapt to the symptoms caused by wearing such an image transposing device.
Several image transposing systems are available in the art. Presently available image transposing devices, however, have several deficiencies for use as a research tool. Some of the major disadvantages of presently available systems are discussed in detail below. Briefly, presently available image transposing systems are either large and heavy, do an inadequate job of blocking untransposed light, have small fields of view, or other inadequacies.
Systems similar to the system shown in U.S. Pat. No. 2,123,6S2 (Wingate) are housed in spectacles and thus do not block untransposed light. Thus, such systems are not effective in preventing untransposed light from reaching the eyes. That is, some light enters the eyes which has not first passed through the prisms. Such systems are unreliable from an experimental point of view since any effects the wearer experiences cannot necessarily be attributed to viewing transposed images.
Other systems such as the one disclosed by Dolezal in the book Living in a World Transformed, Academic Press 1982, includes a glass prism for transposing images and a helmet as a prism retaining device. This system weighs over 8 pounds placing great strain on the neck of the wearer. The system requires a counterweight to offset the weight of the heavy glass prisms and the heavy prism housing and helmet. In addition, this helmet and counterweight system increases the dimensions of the head by over 50% in all directions which may cause the wearer to unintentionally run into objects with his or her head.
Furthermore, the prism in systems similar to the helmet system described by Dolezal in the above-referenced book often fog up and/or require application of anti-fogging fluid. The fogging in such systems is due to inadequate air circulation around the prism.
Although prisms made of materials such as acrylic are known, such acrylic prisms have been adequate for use in image transposing systems used in psychological studies. Although available acrylic prisms are lightweight they have disadvantages. The most significant problem with prisms made of acrylic or other nonglass materials is the unacceptable level of the optical flatness of the prism. The best available prisms made of a lighter-than-glass material have a surface flatness from 200-400 waves as measured under sodium light. Images seen through these prisms appear blurred and "wavy."
Previously known image transposing devices have other disadvantages. For example, the device disclosed in U.S. Pat. No. 3,039,351 (Spagna) utilizes two prisms. In addition to having a complicated construction, such two-prism devices are prone to cause binocular disparity (double images). The binocular disparity in such systems is caused because of the use of two separate prisms or lenses, one for each eye. Even a slight shift of the prisms creates the double images. As will be recognized by those skilled in the art, binocular disparity defeats the purpose of the device when used as a research tool, viz., clear vision.
Systems such as that shown in U.S. Pat. No. 4,077,703 (Pablio) have very restricted fields of view. Such image transposing devices severely limit or restrict the normal scope of human peripheral vision, thus limiting the usefulness of the device in any use that depends upon or is improved by a large field of view. A restricted field of view is undesirable since it makes performing tasks difficult. This disadvantage is especially significant from an experimental point of view since the effects of viewing transformed images cannot be separated from the effects of a very restricted field of view.
Another image transposing device is disclosed in U.S. Pat. No. 4,353,621 (Geer). Devices such as the one disclosed by Geer must be held in front of the eyes of the user with one or both hands. Thus, the use of one or both hands is obviated in performing desirable or necessary eye-hand coordinating tasks. In addition to limiting the user's ability to perform normally, the user's physical safety may be compromised if holding on or steadying should become necessary when balance is lost.
Another disadvantage of previously known image transposing devices is that the distance from the eyes of the viewer is either fixed and relatively distant or quite unreliably variable and is not alterable (cannot be adjusted). In some available systems, once the prism(s) is (are) fixed in its (their) frame the prism(s) cannot be quickly removed or exchanged, thus making expeditious cleaning impossible. Expeditious cleaning may be particularly important in instances where the wearer continues to wear the frame of the goggles. Further, if the prism(s) is non-adjustable in the frame, the prism(s) cannot be adjusted for distance, slope, and/or angle relative to the user's eye or head posture.
Further, image transposing devices usually include prisms which have a relatively sharp prism edge which can abut the nose of the viewer. This sharp edge has several disadvantages. First, the sharp edge can create irritation or damage to the nose. Further, the sharp edge necessarily limits how close the prism can be moved to the eyes. Finally, the sharp edge renders the scope of the field of view of each viewer variable as a function of that individual's nose size. That is, the scope/size of the field of view of different wearers will be different. Thus, any precise between-subject comparisons in experimental paradigms that seek to compare subject performance characteristics are invalidated.
Therefore, in view of the above, it is a primary object of the present inventions to provide an image transposing system which may be worn for extended periods of time without influencing the symptoms caused by the image transformation.
It is a further object of the present invention to provide a lightweight image transposing system.
It is a further object of the present invention to provide an image transposing system which obviates binocular disparity.
It is another object of the present invention to provide an image transposing system which maximizes the scope of peripheral vision of the wearer.
It is a further object of the prevent invention to provide an image transposing system which yields reliable inter-subject comparisons by permitting comparable field of view size for different subjects.
It is a further object of the present invention to provide an optically flat polymer surface, creating clear visual images.
It is still a further object of the present invention to provide an image transposing system that permits easy adjustment and removal or exchange of the system's prism(s).